Feces from healthy humans contains live viruses, most of which are plant viruses that have the ability to sicken and deform plants, according to a study published in the current Public Library of Science Biology journal.

The finding could lead to warnings about the use of human waste as fertilizer. Collected water, otherwise known as "reclaimed" or "gray" water, may also contain deadly plant viruses, but future studies are needed to determine if such water, which is sometimes used for irrigation, can infect plants.